li {
    position: absolute;
    z-index: 1;
    width: 62px;
    background-repeat: repeat-y;

    .pipe_head {
        position: absolute;
        left: 0;
        width: 100%;
        height: 60px;
    }

    &.top_pipe {
        top: 0;
        background-image: url("@images/flappyBird/up_mod.png");

        .pipe_head {
            bottom: 0;
            background-image: url("@images/flappyBird/up_pipe.png");
        }
    }

    &.bottom_pipe {
        bottom: 0;
        background-image: url("@images/flappyBird/down_mod.png");

        .pipe_head {
            top: 0;
            background-image: url("@images/flappyBird/down_pipe.png");
        }
    }
}
